For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
Act I
The Sal and Dean saga begins, with idolatry in Denver, followed by some time with Remi Boncoeur in San Francisco, and some Terry goings-on thrown in for good measure.
Act II
The second cross country trip, with excessive drug use (Bull Lee in New Orleans) and the first notions of blatant abandonment in San Francisco. Act II would end with the Cadillac trip to Chicago before the return, once again, to New York.
Act III
The journey to magic South, i.e., Mexico. This act includes many revelations, a deeper look into Dean’s character, and a thought-provoking conclusion on the streets of New York.